First Author:   Sayef Bakari LIEI, University of Tunis El Manar, Tunisia. bakari.sayef@yahoo.fr   école primaire cité des jeunes 1 Gafsa 2100 GAFSA, 2100, Tunisie   +21640479907(Phone) +21640479907(Fax) Second Author: Mohamed Mabrouki Higher Institute of Companies Administration University of Gafsa, Tunisia. mabroukimed@gmail.com   Gafsa, 2100, Tunisia       Third Author: Asma Elmakki Higher Institute of Companies Administration University of Gafsa, Tunisia. asmaelmakki@yahoo.com   Sned, 2100, Tunisia